When weaving with wide looms of the type used to weave paper forming fabrics, the shuttles are extremely large weighing up to five pounds and being slightly less than three feet long. These shuttles are picked through warp sheds which are up to thirty yards in width. In order to propel the shuttle over this distance, it requires a tremendous force from the picking mechanism. Should something interfere with the flight of the shuttle and cause it to leave its path of travel along the race of the sley, the shuttle will tear through the warp yarns forming the shed, breaking literally hundreds of these yarns, and fly uncontrolled through the weave room. This phenomena is called a tear out or a smash out. Such an occurrence is extremely dangerous. It is also extremely expensive as the warp yarns cannot be repaired because the repair would cause marks on the fabric surface which in turn would cause marks on the paper product formed on the paper forming fabric. A smash out results in major down time and extensive waste of materials, both of which are expensive.
A major cause for shuttle smash outs has been determined to be the development of excessive tension in the weft yarn during its passage out of the shuttle during flight. This is usually caused by the yarn becoming entangled and snarled so that it will not pull freely from the bobbin. Because of the strength of the thread used for weaving forming fabrics, the snarled thread jerks the shuttle from its path of flight into a path through the warp threads.
The prior art does not reveal any special attempts having been made to prevent smash outs. U.S. Pat. Nos. 1,924,179 to Cederlund and 2,306,287 to Turner show weft thread cutters associated with the shuttle; however, these patents are concerned with automatic replenishing. U.S. Pat. No. 2,383,239, to Coldwell shows weft tensioning structure also associated with automatic replenishing.
Accordingly, it is an object of this invention to prevent smash outs caused by the failure of the weft thread to run freely out of the shuttle.
Another object of the invention is to prevent excessive tension from developing in the weft thread during picking
Another object of the invention is to provide an excessive tension preventing apparatus which is carried by the shuttle.
Another object of the invention is to provide a weft severing device carried by the shuttle which is activated in response to weft tension during picking.